Knowledge of the pericardium (pericardial sac) dates back to the time of Galen (129-200 A.D.) the Greek physician and anatomist who created the term "pericardium." The pericardium is a conical membranous sac in which the heart and the commencement of the great vessels are contained. Gray's Anatomy (1977 ed.) pp. 457-460. The pericardium is fluid-filled and functions to prevent dilatation of the chambers of the heart, lubricates the surfaces of the heart, and maintains the heart in a fixed geometric position. It also provides a barrier to the spread of infection from adjacent structures in the chest cavity and prevents surrounding tissue(s) from adhering to the heart. The space between the pericardium and the heart, known as the pericardial space, is normally small in volume and the fluid film within it is too thin to functionally separate the heart and the pericardium. It has been observed that when fluid is injected into the pericardial space, it accumulates in the atrioventricular and interventricular grooves, but not over the ventricular surfaces. See, Shabetai R., "Pericardial and Cardiac Pressure", Circulation, 77:1 (1988).
Pericardiocentesis, or puncture of the pericardium, heretofore has been performed for; 1) diagnosis of pericardial disease(s) by study of the pericardial fluid; 2) withdrawal of pericardial fluid for the treatment of acute cardiac tamponade; and 3) infusion of therapeutic agents for the treatment of malignant effusion or tumors. During 1994, it was estimated that approximately 12,000 pericardiocentesis procedures were performed in the United States and that less than 200 of these patients underwent therapy with the intrapericardial injection of drugs. At present, intrapericardial injection of drugs is clinically limited to the treatment of abnormal pericardial conditions and diseases, such as malignant or loculated pericardial effusions and tumors. Drugs that have been injected into the pericardial space include antibiotic (sclerosing) agents, such as tetracycline, bleyomycin and streptokinase.
Intrapericardial drug delivery has not been clinically utilized for heart-specific treatments where pericardial pathology is normal, because the pericardial space is normally small and very difficult to access without invasive surgery or risk of cardiac injury by standard needle pericardiocentesis techniques. Normally, pericardiocentesis procedures are carried out by highly specialized, experienced personnel in the cardiac catheterization laboratory of medical facilities, assisted by fluoroscopy and electrocardiogram monitoring equipment.
Electrocardiographic monitoring of the procedure using the pericardial needle as an electrode is commonly employed, as disclosed in Bishop L. H., et al., "The Electrocardiogram as a Safeguard in Pericardiocentesis", in JAMA, 162:264 (1956), and Neill J. R., et al., "A Pericardiocentesis Electrode", in The New England Journal of Medicine, 264:711 (1961); Gotsman M. S., et al. "A Pericardiocentesis Electrode Needle", in Br. Heart J., 28:566 (1966); and Kerber R. E., et al., "Electrocardiographic Indications of Atrial Puncture During Pericardiocentesis", in The New England Journal of Medicine, 282:1142 (1970). An echocardiographic transducer with a central lumen has also been used to guide the pericardiocentesis needle, as reported in Goldberg B. B., et al., "Ultrasonically Guided Pericardiocentesis", in Amer. J. Cardiol., 31:490 (1973).
However, there are complications associated with needle pericardiocentesis. These complications include laceration of a coronary artery or the right ventricle, perforation of the right atrium or ventricle, puncture of the stomach or colon, pneumothorax, arrhythmia, tamponade, hypertension, ventricular fibrillation, and death. Complication rates for needle pericardiocentesis are increased in situations where the pericardial space and fluid effusion volume is small (i.e. the pericardial size is more like normal).
U.S. Pat. No. 5,071,428 (Chin, et al.) discloses a method and apparatus for accessing the pericardial space for the insertion of implantable defibrillation leads. This method requires gripping the pericardium with a forceps device and cutting the pericardium with a scalpel (pericardiotomy) under direct vision through a subxiphoid surgical incision.
Uchida Y., et al., "Angiogenic Therapy of Acute Myocardial Infarction by Intrapericardial Injection of Basic Fibroblast Growth Factor and Heparin Sulfate", in Circulation AHA Abstracts (1994) reported a method for the intrapericardial injection of angiogenic agents. While not described in detail, this method generally involved the percutaneous transcatheter bolus injection of drugs into the pericardial cavity via the right atrium. A major drawback of this method is that the right atrial wall is crossed, that could lead to bleeding into the pericardial space. In addition, the method involved the bolus injection of drugs rather than long-term delivery via a catheter or controlled release material.